<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <!--设备的完美视口：改变视口大小-->
    <meta name="viewport" content="width=device-width">
    <title>完美视口</title>
    <style>
        .box1{
            width: 100px;
            height:100px;
            background-color: chartreuse;
        }
    </style>
</head>
<body>
    <div class="box1"></div>
</body>
</html>